Production of cast refractories



Sept. v30, 1941. H. T. sMYTH PRODUCTION OF CAST REFRACTORIES Filed Dec.7, 1939 ing.

Patented Sept. 30, 1941 PRODUCTION F CAST IEFRACTORIES Harold T. Smyth,Louisville, Ky., assi Corhart Refractories Company, Louis. e, Ky., acorporation of Delaware Application December 7, 1939, Serial No. 308,062

6 Claims.

Useful refractories can be made by electrically melting refractorycompositions and casting to shape in suitable molds. During thesubsequent cooling. the liquid resolidies to a non-porous highlycrystalline refractory, the crystallization proceeding gradually inwardfrom each mold surface in proportion to the latent heat dissipated fromthat surface. Since however the volume of any crystalline refractorymaterial is less than the volume occupied when melted, a pipe will beproduced if the mold is just; filled. This internal flaw in a casting isobviously objectionable for any refractory which is required to resistfailure by corrosion, as, for example, glass refractories.

It is the purpose of this invention to provide an economical method ofdecreasing the size of this pipe or of increasing the useful thicknessof refractory material surrounding it.

One method of decreasing thepipe is to supply additional molten materialfrom a font reservoir above the gate which additional material can draininto the casting after partial solidiication has occurred. Thistechnique is limited by the fact that the font casting is also freezingat substantially the same rate as the main casting, so

ISerial Number 166,155 by Fulcher are described various methods ofchanging the location of the pipe after casting the block in its usualposition, as a result of subsequent tilting', rocking or turning of thecasting. In the illustration cited above for example, the block would becast onrits 18" x 40" face to place the gate scar on the back of theblock, and the casting then tilted after the font has drained, so thatvafter partial contraction of volume occurs, the still molten materialin the interior of the elevated end will drain down and ll the center ofthe block. The

that in order for molten material to be availeconomical, and in practicea font with perhaps 10% of the volume of the casting is normallyemployed. This is relatively efficient however as the greatest volume ofthe block is in the outside shell which freezes relatively rapidly. Inthe case of a sphere for example, Va of the volume has frozen when thediameter of the molten core is halved.

As the material frozen in the font itself is wasted, two or more smallfonts may be poured successively. In practice only two fonts areordinarily used because of the difculty of breaking through the gateinto the pipe to permit refill- Metal thus poured into the pipe willitself decrease in `volume upon freezing and leave a smaller pipe sothat the defect is not entirely corrected. K An alternative attack onthe problem of minimizing the danger of failure through the Apipe is tochange its location within the block to a positon where failure is not.as likely to occur ir the particular use to which the block is put.Thus, for a block designed for use in the sidewall of a glass tank,which is often made/18" wide, 12" thick and of a length depending on thedepth of block in use Would then stand on the end` containing the pipewhich however has a smooth and relatively thick shell which was frozenbefore the block was tilted.

Ihav now discoveredthat castings can be made combining the tiltingtechnique with' the relling technique which are improved to anunanticipated degree in that the completeness of refilling is greater ina tilted block than in the usual horizontal casting. L

Referring to the accompanying drawing lin which corresponding parts aredesignated by similar marks of reference, y

Figure 1 illustrates the "present accepted practice of castiig a blockshowingthe character of the pipes resulting therefrom.

Figures 2, 3 and 4 illustratesuccessive steps in casting a block inaccordance with this invention, and Q Figure 5 is a section through ablock cast in accordance with this invention..

The surprising results before referred to as resulting from thisinvention have been traced to the character of the pipe obtained in thetwo cases. 'For example, I refer to Figure 1 in which l represents thefont shell afterdrining; 2 repre-'- sents the pipe resulting from thecontraction upon freezing; v3 represents the solidied area .of therefractory; 4 the mold in which the block has been poured; and 5 thefont mold used for refilling: In a rectangular side wall block such ashere represented, say, 12" x 18" x 42" which is normally poured 12"deep. crystallization and freezing will proceed inward from all sides aslong as the font continues todrain. After the font has drained the levelof the liquid drops on further contraction, to form the pipe, andcrystallization proceeds from the sides and bottom and ends at ratesdepending on the insulation applied. I'he pipe produced in thishorizontal casting is therefore relatively large in area but perhapsonly an inch deep. Furthermore the pipe is generally not a uniformcavity but is likely to have cross fins and thin septa which may resulteither from slopping of the liquid as the casting is handled, or to someununiformity in insulation or some freak of crystal growth. At any ratethe passages within the pipe are narrow and devious.

Refractory material as melted in contact with unmelted batch is onlyslightly superheated above its freezing point and rapidly freezes o ncoming in contact with a colder surface. When such material is pouredinto the relatively thin pipe, 2, of Figure l of'a casting poured in ahorizontal position, this rapid congealing may clog the pasageways on aslow pour, or the molten material may trap air in pockets on a fast pourso that in either case the farthest recesses may be only incompletelylled. As the main purpose of the procedure is to extend the thicknessof' solid refractory and especially towards at least the end which willbe used at the glass line, the purpose is to a certain extent thwartedby the continued presence of ilawsin unknown positions.

On the other hand when such a casting is tilted in order to locate thepipe in one end, the area of the free liquid surface is distinctlydecreased. Since the volume of the pipe will remain the same, the depthis necessarily greater resulting in a more readily filled pipe. Whenmolten material is poured into the concentrated pipe resulting fromcooling in a tilted position, the efficiency of refilling issignificantly increased and no unfilled voids are left in the lower partof the original pipe. The resultant castingV smaller than can beobtained by refilling a cast-v ing cooled in a horizontal position.

To illustrate my method in greater detail the procedure for casting aglass tank sidewall block will be described. The mold is placed with itslong axis horizontal. 'I'he font mold instead of being placed in thecenter can be advantageously shifted toward the end which is to beelevated since the angle of tilt can be increased without preventingdrainage of the font liquid. Without removing the font, the block isthen tilted a few minutes later at such an angle, as illustrated in Fig.2, that molten material can drain simultaneously.from the font and fromthe elevated end of the block as contraction occurs. To prolong thisfont draining period and decrease the.

amount of material wasted by freezing in the font itself, it isadvantageous to cover the font as well as the block with insulatingpowder 6 to retain the heat. After the interior of the block has largelysolidified leaving the pipe, 2", in the position shown in Fig. 3, thefont shell is broken off, the hole into the pipe enlarged by chippingwith a bar, a fo'nt mold 5 placed in position around the hole and thepipe then filled with the casting in a horizontal position as shown inFig. 4. In practicel very little draining occurs from the second fontand it need not be large. A few minutes are suficient to freeze asealing layer on the font thick enough to lwithstand the liquid pressureand the block is then placed again in a tilted position. Since the fontdrainage in this case need notv be taken into consideration, the angleof tilt may be increased ifdesired. Final cooling in this position willgive a small pipe, 2, in the position illustrated in Fig. 5.

The weight of the block is an indication of the.

emciency of refilling, and in practice it is found that heavier blocksare obtained by my procedure.

rIn general the method can be applied with good results whenever tiltingsignificantly decreases the area of the free liquid surface of unfrozenmaterial so that a more compact pipe results. As further examples ofthis general classification we may cite the following:

l. It is desired to manufacture a block to be placed lengthwise in thetop course of a. glass tank sidewall. Since the severest corrosionoccurs at the glass line, the least harmful position for the pipe wouldbe on the bottom outside edge. If the block is say 18" high, 12" thick,and 24 long it would be poured on the 18x24" surface and the 18" axisthen tilted up from the horlzontal to concentrate the pipe along theraised 24" long edge. While the pipe would still be long, its width ismaterially decreased and its depth increased by the tilting so that acompact readily 'led void is formed. The refilled casting is set in thetank with its gate scar out and the edge containing the pipe, down.

2. It is desired to manufacture a doghouse corner in one course. In thiscase the edge projecting into the tank is severely corroded by freshbatch and the least harmful position for the pipe is diagonally oppositeand toward the bottom. If the block is say 18,x18 and 40 high it wouldbe poured on an 18'fx40" surface and then one corner of this surfacewould be raised. In this case the free surface area is decreased inlength as well as width and leaves a -compact pipe for refilling. Thecasting is set in the tank with the corner containing the pipe down andaway from the glass.

What I claim is:

1. 'I'he method of producing a cast refractory comprising casting theblock with font reservoir of insuflicient volume to prevent pipeformation through an asymmetrically located font on top of the block,tilting the block to raise the font end thereof in respect to theopposite end after partial but before complete solidication, breakingthrough the crusts over the pipe and refilling the void left by thecontraction of the first cast material.

2. 'I'he method of producing a cast refractory comprising casting theblock .with font reservoir of insufficient volume to prevent pipeformation through an asymmetrically located font on top of the block,tilting the block to raise the font end thereof in respect to theopposite end after partial but before complete solidiflcation, breakingoff the font shell left by the said casting operation and refilling thethereby exposed pipe resulting from the contraction of the originallycast meterial.

3. I'he method of producing a cast refractory comprising casting theblock through an asymmetrically located font with the gate bearingsurface horizontal, and with a font reservoir of insuflcient volume toprevent lpipe formation, tilting the block to raise the font end thereofin respect to the opposite end after partial but originally castmaterial to a position lower than the gate and refilling the void.

4. The method of producing a cast refractory comprising casting theblock through an asymmetrically located font with the gate bearingsurface horizontal, and.A with a font reservoir of insufcient volume toprevent pipe formation, tilting the block to raise the font end thereofin respect to the opposite end after partial but before completesolidiflcation, breaking -off the font shell left by said castingoperation, thereby exposing the pipe, turning the void left by theoriginally cast material to a position lower than the gate and refillingthe void.

. 5. The method of producing a cast refractory comprising casting theblock through an asymmetrically located font with the gate bearingsurface horizontal, and with a font reservoir of insufficient volume toprevent pipe formation, tilting the block to raise the font end thereofin respect to the opposite end after partial but before completesolidification, exposing and turning the void left by the contraction ofthe originally cast material to a position lower than the gate, rellingthe void, allowing the surface of the added material to solidify andrestoring the block to its first tilted position.

6. 'Ihe method of producing a cast refractory comprising casting theblock through an asymmetrically located font with the ,gate bearingsurface horizontal, and with a font reservoir of in suicient volume toprevent pipe formation, tilting the block to raise the font end thereofin respect to the opposite end after partial but beflore completesolidification, breaking o the font shell left by said. castingoperation thereby exposing the pipe, turning the void resulting from thecontraction of the originally cast material `lower than the gate,refilling the void, allowing the surface of the added material tosolidify and restoring the block to its first tilted position.

' HAROLD T. SMYTH.

